OXALATE CONCENTRATION IN FEEDS AND ITS METABOLISM BY PONIES

Total oxalate and calcium determinations were made in 200 feed samples. Legume hays contained more oxalate than legume-grass, grass (including brome and timothy), native grass and cereal hays (P < 0.05). Grass, native and cereal hays contained low calcium and low to moderate oxalate concentrations. Based on molar ratios and the assumption of preferential binding of calcium by oxalate, it was estimated that about 25% of calcium in legume and legume-grass hays could be bound by oxalate. Similarly, oxalate might bind 38–44% of the calcium contained in native grass and cereal hays and would exacerbate the low calcium content of these hays. Only one hay, a kochia, had oxalate concentrations (3.2%) known to cause acute toxicity in livestock. Oxalate concentration was positively correlated to calcium concentration (r = 0.69). Chopped alfalfa, oat, brome, and slough hay and pelleted alfalfa, oat and barley hays were fed to ponies in two separate Latin square experiments. Apparent oxalate digestibilities were determined to be 48–88%. Cereal hays had the highest apparent oxalate digestibilities in both trials (73–88%) (P < 0.05). Key words: Oxalate, calcium, forages, ponies

DETERMINING AMMONIUM OXALATE-EXTRACTABLE Si IN SOILS

Determination of oxalate-extractable Si and Al is useful in assessing the degree of accumulation of allophane-like materials in Podzolic soils. Three procedures were tested for determining Si: manual spectrophotometry, automated spectrophotometry and atomic absorption. For concentrations of oxalate-extractable Si above 0.5 g kg−1, there was no significant difference among results by the three procedures. For lower concentrations of Si, results by atomic absorption were higher than those by the spectrophotometric procedures. Determination by Si by autoanalyzer is the preferred procedure as it is convenient, sensitive and reliable. Key words: Oxalate Si, Podzolic soil, autoanalyzer